code: def line_separator(line1, line2, block_type, is_continuation=False):
      # Should cover latin-derived languages and russian
      lowercase_letters = "a-zà-öø-ÿа-яşćăâđêôơưþðæøå"
      uppercase_letters = "A-ZÀ-ÖØ-ßА-ЯŞĆĂÂĐÊÔƠƯÞÐÆØÅ"
      # Remove hyphen in current line if next line and current line appear to be joined
      hyphen_pattern = re.compile(
          rf".*[{lowercase_letters}][-]\s?$", re.DOTALL
      )
      if (
          line1
          and hyphen_pattern.match(line1)
          and re.match(rf"^[{lowercase_letters}]", line2)
      ):
          # Split on — or - from the right
          line1 = re.split(r"[-—]\s?$", line1)[0]
          return line1.rstrip() + line2.lstrip()
  
      lowercase_pattern1 = re.compile(
          rf".*[{lowercase_letters},]\s?$", re.DOTALL
      )
      lowercase_pattern2 = re.compile(
          rf"^\s?[{uppercase_letters}{lowercase_letters}]", re.DOTALL
      )
      end_pattern = re.compile(r".*[.?!]\s?$", re.DOTALL)
  
      if block_type in ["Title", "Section-header"]:
          return line1.rstrip() + " " + line2.lstrip()
      elif (
          lowercase_pattern1.match(line1)
          and lowercase_pattern2.match(line2)
          and block_type == "Text"
      ):
          return line1.rstrip() + " " + line2.lstrip()
      elif is_continuation:
          return line1.rstrip() + " " + line2.lstrip()
      elif block_type == "Text" and end_pattern.match(line1):
          return line1 + "\n\n" + line2
      elif block_type == "Formula":
          return line1 + " " + line2
      else:
          return line1 + "\n" + line2
  
file_path: pdf-to-markdown/marker/markdown.py
imports: from marker.schema import MergedLine, MergedBlock, FullyMergedBlock, Page
  import re
  from typing import List
label_desc: Use image node_id 4 for calling a global function with example usage: line_separator(line1, line2, block_type, is_continuation) and returns: unknown, unknown, unknown, unknown, unknown, unknown, unknown